This is a really interesting topic and one I think that spans pre- and post-16 education as well as HE.
Stephen writes of the use of "text language" rather than more formal written English and Hannah has described it as a problem. This issue has also got a national profile in the UK (see Examiner's warning over exams culture).
Part of me really likes text language or txtspk (but aka SMS language) as it’s a variety of language that is totally fit for purpose (i.e. writing quickly and comprehensibly, often on a small keyboard, whilst standing up etc.) as well as being quite creative.
So txtspk is gr8 for instant messaging and SMS on mobiles but should it be used for discussion forums (fora?) where participants have more time to reflect and to produce a more controlled form of written English?
I’m not sure.
What I do think is a problem though is an inability to differentiate between different linguistic registers and to appreciate why some are more appropriate to certain situations than others.
"Hi m8 ru goin pub 2nyt" is fine as an SMS to a friend
"When a number is divided by another number that is gr8er than its square root …" is inappropriate if used in an answer to a formal examination paper.